1. Field of the Invention
The present invention relates to an electronic musical instrument, and more particularly to an electronic musical instrument having an automatic key designating function by which a desirable key for the music to be performed is automatically designated based on chord performance information.
2. Prior Art
With the progress in an automatic technique of an electronic musical instrument and the like, several automatic accompaniment apparatuses have been developed in recent years. Such automatic accompaniment apparatus automatically generates additional tones such as duet tones, arpeggio tones, bass tones etc. based on melody performance, chord performance etc. These additional tones are automatically sounded with performance tones such as a melody tone and chord. Thus, the music can be performed with much variety in its performance manners. In this case, the additional tone can be generated based on the chord only. However, in order to generate the additional tone suitable for the tune to be performed, it is desirable to set the key (such as major key, minor key etc.) of the tune.
Therefore, U.S. Pat. No. 4,419,916 discloses the electronic musical instrument which, prior to the performance, designates the key by operations of a minor key switch and keys of keyboard (hereinafter, referred to keyboard keys). For example, when the performer simultaneously operates a major key switch and a keyboard key corresponding to a C note, the C major key is designated.
However, in the above-mentioned conventional electronic musical instrument, the performer must designate the key by himself. Therefore, this is disadvantageous in that the preparation of the performance becomes troublesome for the performer due to such key designation. In addition, if the performer does not know the key of the tune, the performer can not designate the key. Further, the above key designation is made by using the keyboard, so that the key designation can not be made in the middle of the performance. Furthermore, it is impossible to effect a modulation (i.e., change of key) in the middle of the performance.
Meanwhile, Japanese Patent Laid-Open Publication No. 61-292692 discloses the automatic accompaniment apparatus which automatically generates accompaniment tones such as the arpeggio tones, bass tones etc. This apparatus provides an accompaniment pattern memory for storing pitch difference data indicative of a pitch difference between certain tone and root of chord in accordance with the rhythm progression by each rhythm kind and each chord type. Then, in response to the selected rhythm and the type of chord which is performed by the keyboard, the pitch difference data is read from the accompaniment pattern memory in accordance with the rhythm progression. By adding the read pitch differece data to root note data indicative of the root of chord to be performed, accompaniment tone data indicative of the tone pitch of the accompaniment tone is formed. Thus, the accompaniment tone indicated by the accompaniment tone data is to be sounded.
However, in the above conventional apparatus, the read-out of the pitch difference data from the accompaniment pattern memory is controlled by the rhythm kind and chord type only. Therefore, in order to prevent the musically inadequate accompaniment tone from being sounded, the pitch difference data which can be stored in the accompaniment pattern memory and used for generating the accompaniment tone must be limited to that indicative of the notes such as a basic constituent note and a tension note concerning the chord to be performed. As a result, the accompaniment tone to be generated may be suitable for the ordinary music. However, the succession of accompaniment tones sounds monotonous, thus this conventional apparatus is disadvantageous in that the accompaniment full of variety can not be obtained.
U.S. Pat. No. 4,184,401 discloses the electronic musical instrument which detects the chord in response to the combination of plural note name information. This conventional electronic musical instrument provides a shift register having twelve bits each corresponding to each note of the 12-note scale. In this case, "1" is set to the bit positions of the shift register corresponding to the plural note names which are designated by simultaneously depressing the keyboard keys. Then, until the combination of parallel outputs from the shift register coincides with any one of predetermined combinations each indicative of each of predetermined chord types (such as major, minor, seventh etc.), a series of data stored at the bits of the shift register is circulatingly shifted. When the above combination coincides with that of certain chord type, this chord type is selected. In addition, in response to the circulatingly bit-shifting times of the shift register, the root of chord is determined. Thus, the chord is detected in response to the combination of depressed keyboard keys.
In the above conventional electronic musical instrument, the chord is determined at the firstly detected combination in the circulatingly bit-shifting of the shift register. Therefore, if another combination to be detected exists, such combination must be neglected. So, if the firstly detected combination corresponds to the chord to be selected by the performer, there is no problem. However, if not, the wrong chord is detected. Particularly, in the case where many kinds of chord types are set in the apparatus of U.S. Pat. No. 4,184,401 or the performer designates the chord including the tension note, there are complicated combinations among the note names. Therefore, as the number of the chord types and the notes to be designated becomes larger, the frequency of errors (i.e., wrong detections) becomes larger. Further, when the performer touches or depresses the keyboard key by mistake, this frequency becomes further larger.
When the above wrong detection of the chord is occurred, the third apparatus can not generate the correct automatic accompaniment tones such as the arpeggio tones, bass tones etc. which are generated in response to the detected chord. Therefore, the above conventional electronic musical instrument is disadvantageous in that its quality of the automatic accompaniment tone must be lowered.